1. Field of the Invention
The invention relates generally to valves and more particularly to valves installed for diagnosing failures in engine lubrication systems.
2. Description of the Prior Art
In internal combustion engines, particularly of the type employed in land vehicular propulsion, it has become customary to monitor the pressure of the engine lubrication system and to inform the engine operator of the monitored pressure or of a reduction in pressure below a predetermined minimum valve. This communication to the operator is, of course, intended to prevent unlubricated engine operation. Certain problems have been noted, however, in servicing engines or vehicles in which an indication of insufficient pressure has been noted. These relate to the fact that the sensing of reduced system pressure is indicative of more than one mode of failure in the lubrication system, some of which may be major failures such as failure of the engine oil pump itself, or failure, or impending failure of engine bearings. It may, however, merely indicate failure of the pressure monitoring portion of the system, a relatively minor failure. Since diagnosis of lubrication system failures has customarily been effected by removal and replacement of possibly causative components until the low pressure indication has been eliminated, there has been a danger of overlooking impending bearing failure and/or removal and replacement of non-deflective components such as engine lubrication pumps. This is an expensive, time consuming, undesirable occurrence which is brought about by the inability of service personnel to safely and effectively test an engine driven lubrication pump in its assembled operating condition. This inability arises from the fact that to check one of the prime failure indicia of the pump, its volumetric efficiency, in a simple, effective manner, it is necessary to block the pump outlet and check its capacity to build pressure to a desired level. No provisions are made to affect this blockage in engine installations, and, furthermore, blockage of excessive duration will result in damage to an engine operating without lubricating oil being supplied.